[unreadable] Near-infrared spectroscopy (NIRS) is a promising tool, being the only imaging technique potentially sensitive to both neuronal activity (fast signal) and brain hemodynamics. Our proposal is a response to RFA-EB-05- 001 and aims to demonstrate the ability of NIRS to non-invasively monitor neural activity using methods that may be suitable for functional brain imaging in populations with developmental disorders. Our recent data show that a task-related fast NIRS signal can be recorded non-invasively from the human scalp and that the signal-to-noise ratio of the faint fast optical signal can be improved through a multi-step signal processing sequence that includes 1) adaptive filtering, 2) high-pass temporal filtering, 3) time-frequency decomposition, and 4) Independent Component Analysis. As a result, functionally relevant transient changes in the optical signal within multiple frequency bands (e.g., theta and gamma frequency bands) can be reliably recorded with a temporal resolution in the millisecond range. These changes in neuronal activity can then be mapped through reconstruction techniques with a spatial resolution comparable to that seen with fMRI techniques. Thus, the fast optical imaging of neuronal activity can potentially achieve both good temporal and spatial resolution. The aims of the proposed project are: 1) to develop a sensor net accommodating up to 256 electrodes and optical detectors, allowing full head coverage and simultaneous recording of optical and EEG signals; 2) to develop improved instrumentation and analysis methods in order to reliably detect the fast NIRS signal; 3) to develop improved methods for brain imaging based on the fast optical signal; and 4) to demonstrate that the fast optical signal closely correlates with neuronal activity through simultaneous recording of optical and high-density EEG signals in autistic and control subjects performing tasks involving visual and sensorimotor processing, such as object recognition or response competition. The proposed studies will advance, test and characterize the functional capabilities of the non-invasive fast NIRS technology as well as will establish its potential utility in the analysis of the neural mechanisms underlying visual and sensorimotor processing in health and disease. [unreadable] [unreadable] [unreadable]